Tory MPs have been submitting letters of no confidence for months, with the chairman of the backbench 1922 Committee announcing on Wednesday morning that the threshold of 48 letters has been reached and exceeded

How do MPs trigger a vote of no confidence?

Under current rules, 15 per cent of Tory MPs must write to the chairman of the 1922 Committee, Sir Graham Brady, to trigger a vote of no confidence in Mrs May. This means 48 letters are needed.

Once this threshold has been reached, the committee is then required to consider and hold a vote.

Some Eurosceptic MPs have been open about their letters.

Sir Graham refused to tell journalists how many letters he had received beyond stating that the 48 figure had been exceeded and he had “no reason other than to be confident the threshold had been reached”.

He did add however that there had been “traffic in both directions” when it came to the letters, with some MPs removing letters and others submitting them.

When will the vote be held?

Theresa May will have the opportunity to speak to MPs to spell out why they should still have confidence in her ability to lead the party and remain as Prime Minister.

Mrs May will address her parliamentary party at around 5pm and the ballot will be held between 6pm and 8pm on Wednesday evening in the House of Commons.

Sir Graham said he expected the result to be announced at 9pm.

Crucially, Mrs May will be told the result before the rest of the members.

This is an influential committee of all backbench Conservative MPs. They meet every week – when the House of Commons is sitting – to discuss the party’s frontbenchers. The MPs who originally formed it were elected in 1922.

One of the committee’s biggest responsibilities is overseeing the leadership elections within the Conservative Party.

How many Tories are needed to oust her?

All MPs who have the whip are allowed to vote, which includes the chair Sir Graham himself, but not the Speaker of the House John Bercow or deputy speaker Eleanor Laing.

Mrs May will need the support of “50 per cent plus 1” to stay in office. In practice that would be 158 MPs in total, but there are two Tory backbenchers who currently have the whip withheld, namely Charlie Elphicke and Andrew Griffith.

To add to the complexity, a court decision could come on Wednesday on whether Tory Craig Mackinlay overspent in the 2017 general election, which could change the electorate yet more.

If she wins that, she cannot be challenged for 12 months. However if the margin of victory is small her authority may have been fatally wounded.

Without enough backing, she must resign and there would be a leadership contest to pick her replacement.

If several candidates come forward, a secret vote is held among Conservative MPs to whittle down the number. The candidate with the fewest votes is eliminated from the race and then MPs vote again. The process is repeated until only two candidates remain. These MPs then face a postal ballot of the Tory Party membership.

Whoever wins will become the Prime Minister.

If only one candidate comes forward, he or she becomes leader.

How long would a leadership contest take?

It depends on how many candidates put their names forward. Sir Graham said, should it come to pass, that he wants to see the number of candidates whittled down to two as quickly as possible. Once two are decided by a round of ballots among MPs, it goes to a postal ballot of approximate 120,000 Tory members.

Sir Graham refused to say how quickly a leadership election would occur, but it would be expected to go well into the New Year.

Mrs May could remain in the post during the campaign period.

Will MPs vote against May?

Dr Simon Usherwood, a reader in politics at the University of Surrey, says MPs will be considering if there is a clear alternative or successor to Mrs May when deciding whether or not to back her in the ballot.

It has been reported that some Tories are eyeing up the leadership position including Home Secretary Sajid Javid and former Foreign Secretary Boris Johnson.

Bookmakers’ favourites are Mr Johnson and former Brexit Secretary Dominic Raab, followed by Michael Gove and Mr Javid.

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